The oxonium ion generated by allowing a compound having a glycidyl site and a Lewis acid and the like to act is known to undergo ring-opening copolymerization with a cyclic ether such as tetrahydrofuran.
Specifically, a radically polymerizable polyether having a (meth)acryloyl group that is produced by allowing glycidyl (meth) acrylate, tetrahydrofuran, and boron trifluoride diethyl ether complex of a Lewis acid to act is disclosed in Patent Document 1. In addition, it is disclosed that the polymer composed of the radically polymerizable polyether becomes a resin exhibiting excellently balanced transparency, weather resistance, elastic modulus, and flexibility by setting the number average molecular weight the radically polymerizable polyether to from 300 to 3000 and the amount of (meth)acryloyl group introduced thereinto to from 20 to 98% by mole.
In addition, a radically polymerizable polyether (Table 1. in page 3184) which has the same backbone as that in Patent Document 1, a mass average molecular weight of from 7,900 to 18,500, a number average molecular weight of from 3,300 to 10,300, and an amount of (meth)acryloyl group introduced of from 2.5 to 5.3% by mole, a graft type block copolymer that is composed of the radically polymerizable polyether and methyl methacrylate and soluble in a solvent, and a film that is fabricated by solvent casting the graft type block copolymer are disclosed in Non-Patent Document 1.